Treatment of liver disease with orthotopic liver transplantation (OLT) carries considerable morbidity and mortality. Moreover, due to organ shortages, thousands of people die each year without getting transplanted. Therefore, safer and more convenient alternative therapies will benefit many people requiring liver transplantation. An approach that might address this problem is the development of a proliferative cell line that expresses liver-specific genes which could be employed for cell transplantation or for a bioartificial liver. Developing such a line from human embryonic stem cells (ESC) would provide cells valuable for pharmacology and toxicology studies, as well as establishing an approach that could be employed in human cells. Specific Aims: 1) to determine conditions for directing the ESC to differentiate into hepatocytes in vitro, and to characterize the differentiated cells; and 2) to establish the in vivo potential of human ESC. Methods: A variety of conditions will be empirically assayed to delineate the most effective approach to differentiate the embryonic cells along a hepatocyte lineage. The NIH code number of the cells that are being used is WA01. To delineate mechanisms aimed at inducing either proliferation or hepatocellular gene expression in the cells, specific manipulations will be utilized with assays of liver-specific gene products and growth factor responsiveness. To determine whether the cells can engraft, survive and proliferate after transplantation, studies will be conducted in immunodeficient NOD-SCID mouse models. Health Relatedness: If the studies are successfully undertaken, it will provide for the development of an unlimited source of differentiated human hepatocyte-like cells that can be employed in cell-based therapeutics or in pharmacology studies. [unreadable] [unreadable] [unreadable]